Gear-hobbing machine



S. FEARNS GEAR HOBBING MACHINE March 13, 1951 Filed Jan. 18, 1947 WMA/ Patented Mar. 13, 1951 GEARTHOBBING MACHINE Stanley Fearns, Huddersfield, England, assignor to David Brown & Sons (Huddersfield), Limited, Huddersfield, England Application January 18, 1947, Serial N0. 722,861 In Great Britain January 24, 1946 2 Claims. I

The invention relates to machines for hobbing or generating the teeth of helical gears.

It is usual to drive the rotary worktable of a machine of the kind referred to by providing it with a Worm-Wheel with which meshes, either directly or through intermediate gears, a driving Worm, and it is known to give to this Worm a slow rotation or creep round the axis of the worm-wheel whilst the cuttin operation is in progress. This procedure causes the effects of errors in the worm-wheel, or table gear as it is termed, to be distributed around the work in helices instead of along axial lines.

It is necessary, when a creep motion is provided, to make provision whereby an additional rotation is given to the worm to compensate for its creep about the axis of the table gear, and it is usual to effect this by providing differential gearing in the drive by which the worm is rotated.

The present invention has for its object to provide creep mechanism for a machine, for hobbing or generating the teeth of helical gears, by means of which the use of difierential gearing will be avoided.

In order that the invention may be understood I shall, in describing the same, make reference to the accompanyin drawing which illustrates, in more or less diagrammatic form, the mechanism constituting the invention and its application to a gear-hobbing machine.

Referring to the drawing, l represents a wheel blank in which teeth are to be cut and II a hob for cutting the teeth.

The shaft l2 carrying the hob H is driven by gears l3 and I4, shaft l5, bevels l6, l6, shaft bevels |8, |8, shaft I9, bevels 20, 20, shaft 2|, gears 22, 22', shaft 23 and gears 24, 24, from the shaft 25 of a suitable electric motor 26.

A rotary work table 21 carrying the wheel blank ID has associated with it a table gear 28 driven by gear 29, a worm wheel 36, worm 3|, shaft 32, universal joint 33, shaft 34, universal joint 35, shaft 36, change gearin 31, shaft 38, and gear 39 from the gear 22', which, as above mentioned, receives its motion from the motor 26.

Any alteration in the speed of rotation of the hob H is thus accompanied by a corresponding variation in the rate of rotation of the worktable 21.

The usual feed motion for the hob saddle which, as it forms no part of the present invention is not shown, is taken, in the illustrated example, from a separate motor 40 through gears 4| and 42, shaft 43, change gearing 44, shaft 45, gears 46 and 41, shaft 48, gears 49 and 50 and shaft 5|.

Alternatively, of course, the shaft 48 may be driven from the motor 26 which drives the hob l2 and the work-table 21.

The worm 3| from which the table gear 28 receives its motion, together with the worm wheel 30 and gear 29 intermediate said worm 3| and the table gear is carried by a cradle 52 pivotal about the axis of the worktable. The periphery of the cradle 52 is provided with ear teeth which are engaged by a worm-53 driven through shaft 54, gear 55, change gearing 56, shaft 51 and gears 58 and 59, from the same shaft 45 through which drive is led to the feed motion for the hob saddle. The result of the geared connection between the cradle 52 is that the combined effect of the hob feed and of the rotation of the work table, as infiuenced by the creep given to the table driving worm 3|, gives the desired helix angle to the teeth of the work piece.

The rate of feed given to the hob saddle through the shaft 45 can be changed whilst work is in progress without danger to either the hob or the work, and any such change is accompanied by a corresponding or proportionate variation in the rate of creep.

Having thus described my invention, what claim as new and desire to secure by Letters Patent is:

1. In a gear hobbing machine, a hob and gearing intermediate same and a source of motion, a rotary work table, a worm through which rotary motion is conveyed to said worktable, a shaft carrying said worm, a change gearing, a universally-jointed connection between said shaft carrying said worm and said change gearing, a geared connection between said change gearing and a member of the gear train through which the hob is driven, a cradle pivotal about the axis of the worktable and carrying the worm through which rotary motion is conveyed to the worktable, gear teeth on said cradle, feed motion means for said hob, a driven shaft drivin said feed motion means, and a worm meshing with the teeth on the cradle and driven through gearing from said driven shaft which also drives said feed motion means for the hob.

2. In a gear hobbing machine a hob; means for rotating said hob; a rotary work table; a worm through which rotary motion is conveyed to said work table; a shaft carrying said worm; driving means for rotating said shaft; a cradle pivotal about the axis of said work table and carrying said worm through which rotary motion is conveyed to said work table; gear teeth on said cradle; feed motion means for said hob; a driven 3 shaft drivin said feed motion means; a, worm meshing with said gear teeth on said cradle; and a gearing driven also by said driven shaft and driving said Worm meshing with said gear teeth or; said cradle.

" AMIEY REFERENCES CITED The following references are of record in the file of this patent:

Number Number UNITED STATES PATENTS Name Date Grundstein Aug. 4, 1914 Hodgkinson Oct. 7, 1924 Sykes etia l. Apr. 5, 1949 FOREIGN PATENTS Country Date France Feb. 17, 1941 

